Dicationic Diimine Pt(II) Bis(N-heterocyclic allenylidene) Complexes: Extended Pt···Pt Chains, NIR Phosphorescence, and Chromonics.

Although square-planar Pt(II) complexes are well-known to self-assemble into supramolecules via noncovalent intermolecular Pt···Pt and/or π-π interactions, the self-assembly of dicationic Pt(II) complexes was scarce due to the electrostatic repulsive force. Herein, a series of dicationic diimine bis(N-heterocyclic allenylidene) Pt(II) complexes were synthesized and characterized. Close Pt···Pt and/or π-π contacts are observed in the crystals of these complexes. In particular, complexes 1·2PF6 and 2·2PF6 exhibit one-dimensional packing with extended Pt···Pt contacts of 3.302 and 3.240 Å, respectively. The photophysical properties of these complexes in the solution and solid state were investigated. NIR emission was recorded for complexes 1·2PF6 (λmax = 950 nm) and 2·2PF6 (λmax = 855 nm) in the solid state at 298 K. To explore the aggregate behaviors of these complexes, the counteranion PF6- was exchanged to the large lipophilic anion 2,3,4-tris(dodecyloxy)benzene sulfonate (LA-) and the hydrophilic anion Cl-. Complexes 1·2LA and 2·2LA or 1·2Cl and 2·2Cl could self-assemble with Pt···Pt and/or π-π interactions in the nonpolar or aqueous solutions as well. Further increasing the concentration of 1·2Cl and 2·2Cl in aqueous solution, chromonic mesophases with NIR emission (λmax = 988 nm) were obtained. DFT and TD-DFT calculations were performed to gain deep insight into the dication-dication packings and photophysical properties of the complexes. The σ-donating as well as π-accepting character of the N-heterocyclic allenylidene ligand endows complexes with rigid and electron-delocalized coplanar features, which are conducive to achieving the self-assembling processes associated with Pt···Pt and/or π-π interactions.

Aggregation of phosphorescent Pd(II) and Pt(II) complexes with lipophilic counter-anions in non-polar solvents.

Phosphorescent cationic tridentate C^N^N (HC^N^N = 6-(2-R2,4-R1-phenyl)-2,2'-bipyridine; R1 = R2 = H or F, or R1 = OMe, R2 = H) cyclometallated Pd(II) complexes with an N,N-dimethyl-imidazol-allenylidene ancillary ligand (L) and their corresponding Pt(II) congeners have been synthesized and characterized, following the previously reported preparation of the complex [Pd(6-phenyl-2,2'-bipyridine)L]+. For these cationic Pd(II)/Pt(II) complexes with 2,3,4-tris(dodecyloxy)benzenesulfonate (LA-) counter-anions in mixed CH2Cl2/toluene solvents, uniform square flake or fibre-like aggregates were formed. Corresponding multicolour phosphorescence with obvious metal-metal-to-ligand charge transfer (MMLCT) features gradually changed from red to NIR by manipulating the various fractions of Pd/Pt species. Circular dichroism (CD) and circularly polarized luminescence (CPL) derived from the fibre-like Pd aggregates of [Pd(6-(2,4-difluorophenyl)-2,2'-bipyridine)L]+ in chiroptical CH2Cl2/limonene solvents were achieved with an isodesmic aggregation mode. Dispersive metallophilic interactions are claimed to be the driving force for these photo-functional aggregates.

Palladium-Catalyzed C-H Bond Arylation of Cyclometalated Difluorinated 2-Arylisoquinolinyl Iridium(III) Complexes.

The utility of C-H bond functionalization of metalated ligands for the elaboration of aryl-functionalized difluorinated-1-arylisoquinolinyl Ir(III) complexes has been explored. Bis[(3,5-difluorophenyl)isoquinolinyl](2,2,6,6-tetramethyl-3,5-heptanedionato) iridium(III) undergoes Pd-catalyzed C-H bond arylation with aryl bromides. The reaction regioselectively occurred at the C-H bond flanked by the two fluorine atoms of the difluoroaryl unit, and on both cyclometalated ligands. This post-functionalization gives a straightforward access to modified complexes in only one manipulation and allows to introduce thermally sensitive functional groups, such as trifluoromethyl, nitrile, benzoyl, or ester. The X-ray crystallography, photophysical, and electrochemical properties of the diarylated complexes were investigated. Whatever the nature of the incorporated substituted aryl groups is, all obtained complexes emit red phosphorescence (622-632 nm) with similar lifetimes (1.9-2 µs).

Helically chiral Pd(ii) complexes containing intramolecular PdPd metallophilicity as circularly polarized molecular phosphors.

Carbon-centred chirality of the pincer-type cyclometalated ligands is transferred to the helical chirality of dinuclear and tetranuclear Pd(ii) arylacetylide complexes, and hence phosphorescence with quantum yields up to 50% and dissymmetry factors in the 10-3 scale from the metal-metal-to-ligand charge-transfer excited states has been recorded in diluted solutions.

Highly phosphorescent organopalladium(ii) complexes with metal-metal-to-ligand charge-transfer excited states in fluid solutions.

Dinuclear pincer-type cyclometalated Pd(ii) complexes with foldable diacetylide ligands show crystallographically determined intramolecular PdPd contacts of 3.203-3.380 Å. In deoxygenated fluid solutions, these Pd(ii) complexes are highly phosphorescent in the red region with emission quantum yields up to 48%, which has been ascribed to metal-metal-to-ligand charge-transfer (MMLCT) excited states in nature.

Palladium(ii) N-heterocyclic allenylidene complexes with extended intercationic PdPd interactions and MMLCT phosphorescence.

Extended intercationic PdPd contacts of 3.30 Å in the crystal structure and distinct MMLCT transitions absorbing at 528 nm and emitting beyond 600 nm in solutions have been revealed with cyclometalated Pd(ii) N-heterocyclic allenylidene complexes. The Pd(ii)-based MMLCT excited states are responsive to concentrations, temperatures, mechanical force and organic vapors.

Structure-activity relationship of polypyridyl ruthenium(II) complexes as DNA intercalators, DNA photocleavage reagents, and DNA topoisomerase and RNA polymerase inhibitors.

To investigate the relationship between the molecular structure and biological activity of polypyridyl Ru(II) complexes, such as DNA binding, photocleavage ability, and DNA topoisomerase and RNA polymerase inhibition, six new [Ru(bpy)(2)(dppz)](2+) (bpy=2,2'-bipyridine; dppz=dipyrido[3,2-a:2,',3'-c]phenazine) analogs have been synthesized and characterized by means of (1)H-NMR spectroscopy, mass spectrometry, and elemental analysis. Interestingly, the biological properties of these complexes have been identified to be quite different via a series of experimental methods, such as spectral titration, DNA thermal denaturation, viscosity, and gel electrophoresis. To explain the experimental regularity and reveal the underlying mechanism of biological activity, the properties of energy levels and population of frontier molecular orbitals and excited-state transitions of these complexes have been studied by density-functional theory (DFT) and time-depended DFT (TDDFT) calculations. The results suggest that DNA intercalative ligands with better planarity, greater hydrophobicity, and less steric hindrance are beneficial to the DNA intercalation and enzymatic inhibition of their complexes.